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Chapt13lecture 1227038200640866-8
- 1. Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Chapter 13 Lecture Outline
- 2. Learning Outcomes After studying this chapter, you should be able to answer the following questions: • What are the major components of the waste stream? How do we dispose of most of our waste? • How does a sanitary landfill operate? Why are we searching for alternatives to landfills? • Why is ocean dumping a problem? • What are the benefits of recycling? • What are the “three Rs” of waste reduction, and which is most important? • What are some steps you can take to reduce waste production? • How can biomass waste be converted to natural gas? • What are toxic and hazardous waste? How do we dispose of them? • What is bioremediation? Is it a promising solution in waste management? • What is the Superfund, and has it shown progress? 13-2
- 3. We are living in a false economy where the price of goods and services does not include the cost of waste and pollution. –Lynn Landes, founder and director of Zero Waste America 13-3
- 4. 13.1 Waste • We all produce unwanted byproducts and residues in nearly everything we do. • According to the Environmental Protection Agency (EPA), the United States produces 11 billion tons of solid waste each year. • Industrial waste—other than mining and mineral production—amounts to some 400 million metric tons per year in the United States. • Municipal waste—a combination of household and commercial refuse—amounts to about 250 million metric tons per year in the United States. 13-4
- 5. 13-5
- 6. 13-6
- 7. The waste stream • The waste stream is a term that describes the steady flow of varied wastes that we all produce, from domestic garbage and yard wastes to industrial, commercial, and construction refuse. • Many of the materials in our waste stream would be valuable resources if they were not mixed with other garbage. • Unfortunately, our collecting and dumping processes mix and crush everything together, making separation an expensive and sometimes impossible task. 13-7
- 8. 13.2 Waste Disposal Methods • Open, unregulated dumps are still the predominant method of waste disposal in most developing countries. • The giant developing world megacities have enormous garbage problems (fig. 13.4). • Most developed countries forbid open dumping, at least in metropolitan areas, but illegal dumping is still a problem. 13-8
- 9. Ocean dumping is nearly uncontrollable • Every year some 25,000 metric tons (55 million lbs) of packaging, including half a million bottles, cans, and plastic containers, are dumped at sea. • Environmental groups estimate that 50,000 northern fur seals are entangled in this refuse and drown or starve to death every year in the North Pacific alone. 13-9
- 10. Landfills receive most of our waste • Increasingly, cities have turned to sanitary landfills, where solid waste disposal is regulated and controlled. • To decrease smells and litter and to discourage insect and rodent populations, landfill operators are required to compact the refuse and cover it every day with a layer of dirt. 13-10
- 11. Incineration produces energy but causes pollution • Waste incinerators burn municipal waste. • This technology is also called energy recovery, or waste-to-energy, because the heat derived from incinerated refuse is a useful resource. • Refuse-derived fuel is what’s left after unburnable or recyclable materials are removed. • Mass burn is to dump everything smaller than a sofa into a giant furnace. 13-11
- 12. 13-12
- 13. 13.3 Shrinking the Waste Stream • Having less waste to discard is obviously better than struggling with disposal methods, all of which have disadvantages and drawbacks. • The term recycling has two meanings in common usage. – Sometimes we say we are recycling when we really are reusing something, such as refillable beverage containers. – Recycling is the reprocessing of discarded materials into new, useful products. 13-13
- 14. Recycling captures resources from garbage 13-14
- 15. Composting recycles organic waste 13-15
- 16. Reducing waste is often the cheapest option 13-16
- 17. What Can You Do? Reducing Waste 1. Buy foods that come with less packaging; shop at farmers’ markets or co-ops, using your own containers. 2. Take your own washable, refillable beverage container to meetings or convenience stores. 3. When you have a choice at the grocery store among plastic, glass, or metal containers for the same food, buy the reusable or easier-to recycle glass or metal. 4. Separate your cans, bottles, papers, and plastics for recycling. 5. Wash and reuse bottles, aluminum foil, plastic bags, and so on for your personal use. 6. Compost yard and garden wastes, leaves, and grass clippings. 7. Help your school develop responsible systems for disposing of electronics and other waste. 8. Write to your senators and representatives, and urge them to vote for container deposits, recycling, and safe incinerators or landfills. Source: Data from Minnesota Pollution Control Agency. 13-17
- 18. 13.4 Hazardous and Toxic Wastes • The most dangerous aspect of the waste stream is that it often contains highly toxic and hazardous materials that are injurious to both human health and environmental quality. 13-18
- 19. Hazardous waste includes many dangerous substances • Legally, a hazardous waste is any discarded material, liquid or solid, that contains substances known to be: – fatal to humans or laboratory animals in low doses; – toxic, carcinogenic, mutagenic, or teratogenic to humans or other life-forms; – ignitable with a flash point less than 60°C; – corrosive; or – explosive or highly reactive (undergoes violent chemical reactions either by itself or when mixed with other materials). 13-19
- 20. Federal legislation regulates hazardous waste • Two important federal laws regulate hazardous waste management and disposal in the United States. – The Resource Conservation and Recovery Act (RCRA, pronounced “rickra”) of 1976. – The Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA or Superfund Act), passed in 1980 and modified in 1984 by the Superfund Amendments and Reauthorization Act (SARA), is aimed at rapid containment, cleanup, or remediation of abandoned toxic waste sites. 13-20
- 21. 13-21
- 22. Superfund sites are those listed for federal cleanup • There may be over 400,000 “Superfund” sites in the U.S. • Total costs for hazardous waste cleanup in the U.S. are estimated to be between $370 billion and $1.7 trillion. 13-22
- 23. Brownfields present both liability and opportunity • In many cities, there are large areas of contaminated properties, known as brownfields, that have been abandoned or are not being used to their potential because of real or suspected pollution. • Up to one-third of all commercial and industrial sites in the urban core of many big cities fall in this category. 13-23
- 24. Hazardous waste must be processed or stored permanently There are 3 choices regarding the production and handling of hazardous wastes: • Produce less waste As with other wastes, the safest and least expensive way to avoid hazardous waste problems is to avoid creating the wastes in the first place. • Convert to less hazardous substances Several processes are available to make hazardous materials less toxic. • Store permanently: Inevitably, there will be some materials that we can’t destroy, make into something else, or otherwise cause to vanish. 13-24
- 25. A secure landfill for toxic waste 13-25
- 26. Practice Quiz 1. List some items that can be recycled from construction and demolition waste. 2. What are solid wastes and hazardous wastes? What is the difference between them? 3. Describe the difference between an open dump, a sanitary landfill, and a modern, secure, hazardous waste disposal site. 4. Describe some concerns about waste incineration. 5. List some benefits and drawbacks of recycling wastes. What are the major types of materials recycled from municipal waste, and how are they used? 6. What is e-waste? How is most of it disposed of, and what are some strategies for improving recycling rates? 7. What is composting, and how does it fit into solid waste disposal? 8. What materials are most recycled in the United States? 9. What are brownfields, and why do cities want to redevelop them? 10. What are bioremediation and phytoremediation? What are some advantages to these methods? 13-26
Editor's Notes
- In this chapter and throughout this book, you will read about many cases in which humans have caused serious environmental problems. You will also read about promising, exciting solutions to many of these problems. Your task as a student of environmental science is to gain an idea of what some of the larger current problems are, what some solutions might be, and how you might use knowledge from a variety of disciplines—from biology and chemistry to economics—to develop tomorrow’s strategies for more sustainable living on our planet.
- We all produce unwanted byproducts and residues in nearly everything we do. According to the Environmental Protection Agency (EPA), the United States produces 11 billion tons of solid waste each year. Nearly half of that amount consists of agricultural waste, such as crop residues and animal manure, which are generally recycled into the soil on the farms where they are produced. Industrial waste—other than mining and mineral production—amounts to some 400 million metric tons per year in the United States. Most of this material is recycled, converted to other forms, destroyed, or disposed of in private landfills or deep injection wells. About 60 million metric tons of industrial waste fall in a special category of hazardous and toxic waste, which we will discuss later in this chapter. Municipal waste—a combination of household and commercial refuse—amounts to about 250 million metric tons per year in the United States. That’s just over 2 kg (4.6 lbs) per person per day—twice as much per capita as Europe or Japan, and five to ten times as much as most developing countries (fig. 13.2).
- There are organic materials, such as yard and garden wastes, food wastes, and sewage sludge from treatment plants; junked cars; worn-out furniture; and consumer products of all types. Newspapers, magazines, advertisements, and office refuse make paper one of our major wastes (fig. 13.3). In spite of recent progress in recycling, many of the 200 billion metal, glass, and plastic food and beverage containers used every year in the United States end up in the trash.
- The oceans are vast, but not so large that we can continue to treat them as carelessly as has been our habit. Beaches, even in remote regions, are littered with the nondegradable flotsam and jetsam of industrial society (fig. 13.5). Until recently, many cities in the United States dumped municipal refuse, industrial waste, sewage, and sewage sludge into the ocean. Federal legislation now prohibits this dumping. New York City, the last to stop offshore sewage sludge disposal, finally ended this practice in 1992. Still, 60 million to 80 million m3 of dredge spoil—much of it highly contaminated—are disposed of at sea.
- Since 1994, all operating landfills in the United States have been required to control such hazardous substances as oil, chemical compounds, toxic metals, and contaminated rainwater that seep through piles of waste. An impermeable clay and/or plastic lining underlies and encloses the storage area. Drainage systems are installed in and around the liner to catch drainage and to help monitor chemicals that leak out. Modern municipal solid waste landfills now have many of the safeguards of hazardous waste repositories described later in this chapter. Currently, 55 percent of all municipal solid waste in the United States is landfilled, 30 percent is recycled, and 15 percent is incinerated. Suitable places for waste disposal are becoming scarce in many areas. Other uses compete for open space. Citizens have become more concerned and vocal about health hazards, as well as aesthetics. It is difficult to find a neighborhood or community willing to accept a new landfill. Since 1984, when stricter financial and environmental protection requirements for landfills took effect, roughly 90 percent of all existing landfills in the United States have closed. In many cases, this means that old, small, uneconomical landfills closed, while larger, more modern ones replaced them. Nevertheless, many major cities are running out of local landfill space. They export their trash, at enormous expense, to neighboring communities and even other states. More than half the solid waste from New Jersey goes out of state, some of it up to 800 km (500 mi) away.
- Types of incinerators Municipal incinerators are specially designed burning plants capable of burning thousands of tons of waste per day. In some plants, refuse is sorted as it comes in to remove unburnable or recyclable materials before combustion. This is called refuse-derived fuel because the enriched burnable fraction has a higher energy content than the raw trash. Another approach, called mass burn, is to dump everything smaller than sofas and refrigerators into a giant furnace and burn as much as possible (fig. 13.8). This technique avoids the expensive and unpleasant job of sorting through the garbage for nonburnable materials, but it often causes greater problems with air pollution and corrosion of burner grates and chimneys. Incinerators have serious negative consequences. Residual ash and unburnable residues representing 10 to 20 percent of the original volume are usually taken to a landfill for disposal. Because the volume of burned garbage is reduced by 80 to 90 percent, disposal is a smaller task. However, the residual ash usually contains a variety of toxic components that make it an environmental hazard if not disposed of properly. Ironically, one worry about incinerators is whether enough garbage will be available to feed them. Often, incinerators compete with recycling programs for paper, plastics, and other materials. Some communities in which recycling has been really successful have had to buy garbage from neighbors to meet contractual obligations to waste-to-energy facilities. In other places, fears that this might happen have discouraged recycling efforts.
- Incinerator cost and safety The cost-effectiveness of garbage incinerators is the subject of heated debates. Initial construction costs are high—usually between $100 million and $300 million for a typical municipal facility. Tipping fees at an incinerator (the fee charged to haulers for each ton of garbage dumped) are often much higher than those at a landfill. As landfill space near metropolitan areas becomes more scarce and more expensive, however, landfill rates are certain to rise. It may pay in the long run to incinerate refuse so that the lifetime of existing landfills will be extended. Environmental safety of incinerators is another point of concern. The EPA has found alarmingly high levels of dioxins, furans, lead, and cadmium in incinerator ash. These toxic materials are more concentrated in the fly ash (lighter, airborne particles capable of penetrating deep into the lungs) than in heavy bottom ash. Dioxin levels can be as high as 780 ppb (parts per billion). One part per billion of TCDD, the most toxic dioxin, is considered a health concern.
- Wild fluctuations in commodity prices make it still harder to develop a market for recycled materials. Newsprint, for example, cost $160 a ton in 1995; by 1999 it dropped to just $42 per ton and then climbed to $650 per ton in 2006 (fig. 13.10). Contamination is a major obstacle in plastics recycling. Most of the 24 billion plastic soft drink bottles sold every year in the United States are made of PET (polyethylene terphthalate), which can be remanufactured into carpet, fleece clothing, plastic strapping, and nonfood packaging. However, even a trace of vinyl—a single PVC (polyvinyl chloride) bottle in a truckload, for example—can make PET useless.
- The Resource Conservation and Recovery Act (RCRA, pronounced “rickra”) of 1976 is a comprehensive program that requires rigorous testing and management of toxic and hazardous substances. A complex set of rules requires generators, shippers, users, and disposers of these materials to keep meticulous account of everything they handle and what happens to it from generation (cradle) to ultimate disposal (grave) (fig. 13.18). The Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA or Superfund Act), passed in 1980 and modified in 1984 by the Superfund Amendments and Reauthorization Act (SARA), is aimed at rapid containment, cleanup, or remediation of abandoned toxic waste sites. This statute authorizes the EPA to undertake emergency actions when a threat exists that toxic material will leak into the environment. The EPA is empowered to bring suit for the recovery of its costs from potentially responsible parties, such as site owners, operators, waste generators, or transporters. SARA also established (under title III) a community right to know and state emergency response plans that give citizens access to information about what is present in their communities. One of the most useful tools in this respect is the Toxic Release Inventory, which requires 20,000 manufacturing facilities to report annually on releases of more than 300 toxic materials. You can find specific information in the inventory about what is in your neighborhood. The government does not have to prove that anyone violated a law or what role he or she played in a Superfund site. Rather, liability under CERCLA is “strict, joint, and several,” meaning that anyone associated with a site can be held responsible for the entire cost of cleaning it up, no matter how much of the mess they made. In some cases property owners have been assessed millions of dollars for removal of wastes left there years earlier by previous owners. This strict liability has been a headache for the real estate and insurance businesses.
- The EPA estimates that there are at least 36,000 seriously contaminated sites in the United States. The General Accounting Office (GAO) places the number much higher, perhaps more than 400,000 when all are identified. Originally, about 1,671 sites were placed on the National Priority List (NPL) for cleanup with financing from the federal Superfund program. The Superfund is a revolving pool designed to (1) provide an immediate response to emergency situations that pose imminent hazards and (2) to clean up or remediate abandoned or inactive sites. Without this fund, sites would languish for years or decades while the courts decided who was responsible for paying for the cleanup. Originally a $1.6 billion pool, the fund peaked at $3.6 billion. From its inception, the fund was financed by taxes on producers of toxic and hazardous wastes. Industries opposed this “polluter pays” tax, because current manufacturers are often not the ones responsible for the original contamination. In 1995 Congress agreed to let the tax expire. Since then the Superfund has dwindled, and the public has picked up an increasing share of the bill. In the 1980s the public covered less than 20 percent of the Superfund. In 2004, however, general revenues (public funds) paid the entire cost off a greatly reduced program, and the industry share was zero.
- Manufacturing processes can be modified to reduce or eliminate waste production. In Minnesota, the 3M Company reformulated products and redesigned manufacturing processes to eliminate more than 140,000 metric tons of solid and hazardous wastes, 4 billion liters (1 billion gal) of wastewater, and 80,000 metric tons of air pollution each year. It frequently found that these new processes not only spared the environment but also saved money by using less energy and fewer raw materials. Physical treatments tie up or isolate substances. Charcoal or resin filters absorb toxins. Distillation separates hazardous components from aqueous solutions. Precipitation and immobilization in ceramics, glass, or cement isolate toxins from the environment, so that they become essentially nonhazardous. One of the few ways to dispose of metals and radioactive substances is to fuse them in silica at high temperatures to make a stable, impermeable glass that is suitable for long-term storage. Plants, bacteria, and fungi can also concentrate or detoxify contaminants (see Exploring Science p. 324). Incineration is applicable to mixtures of wastes. A permanent solution to many problems, it is quick and relatively easy, but not necessarily cheap—nor always clean—unless done correctly. Chemical processing can transform materials to make them nontoxic. Included in this category are neutralization, removal of metals or halogens (chlorine, bromine, etc.), and oxidation. The Sunohio Corporation of Canton, Ohio, for instance, has developed a process called PCBx, in which chlorine in such molecules as PCBs is replaced with other ions that render the compounds less toxic.
- Secure Landfills: One of the most popular solutions for hazardous waste disposal has been landfilling. Although, as we saw earlier in this chapter, many such landfills have been environmental disasters, newer techniques make it possible to create safe, modern secure landfills that are acceptable for disposing of many hazardous wastes. The first line of defense in a secure landfill is a thick bottom cushion of compacted clay that surrounds the pit like a bathtub (fig. 13.22). Moist clay is flexible and resists cracking if the ground shifts. It is impermeable to groundwater and will safely contain wastes. A layer of gravel is spread over the clay liner, and perforated drainpipes are laid in a grid to collect any seepage that escapes from the stored material. A thick polyethylene liner, protected from punctures by soft padding materials, covers the gravel bed. A layer of soil or absorbent sand cushions the inner liner, and the wastes are packed in drums, which then are placed into the pit, separated into small units by thick berms of soil or packing material. When the landfill has reached its maximum capacity, a cover much like the bottom sandwich of clay, plastic, and soil—in that order—caps the site. Vegetation stabilizes the surface and improves its appearance. Sump pumps collect any liquids that filter through the landfill, either from rainwater or leaking drums. This leachate is treated and purified before being released. Monitoring wells check groundwater around the site to ensure that no toxins have escaped.